Ozone (O3)

Sources:

Ozone is not produced directly by vehicles. Ground-level ozone is produced when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs), such as xylene, react in the atmosphere in the presence of sunlight. NOx and VOCs are called ozone precursors.

Impacts:

Respiratory illness and distress, ozone makes people more sensitive to allergens, which in turn trigger asthma attacks